Which term indicates something vast, impressive, or substantial in extent?

The term that indicates something vast, impressive, or substantial in extent is "prodigious." This word is often used to describe something extraordinarily large or powerful, emphasizing its remarkable scale or greatness. For instance, one might refer to a prodigious talent in a particular field, meaning that the talent is not just significant but exceeds normal expectations.

To contrast with the other options, "pretentious" refers to an attempt to impress by affecting greater importance or merit than is actually possessed. "Prevaricate" means to speak or act in an evasive way, typically in a context of avoiding the truth. "Profligate" describes someone who is recklessly extravagant or wasteful in the use of resources. None of these options convey the meaning of vastness or impressiveness associated with "prodigious."